PROJECT SUMMARY: Disruption in neuronal migration results in severe neurological and developmental impairments such as cognitive deficits and epilepsy that are recognized primarily in the pediatric population. A signaling pathway crucial for proper neuronal migration and brain development is initiated by the evolutionarily conserved glycoprotein Reelin. Human mutations in the Reelin pathway generate phenotypes that mimic those induced by mutations in cytoskeletal proteins that disrupt the function of microtubules and actin. The culmination of these genetic studies in children strongly suggests that several signaling pathways including the Reelin pathway converge on downstream cytoskeletal proteins to affect proper neuronal migration, brain development and cognition. We used a systems biology approach to identify the microtubule-stabilizing CLASP2 as a key cytoskeletal modifier of Reelin signaling. We previously found that CLASP2 regulates several important phenotypes during neuronal development in vitro including Golgi morphology, neuronal branching, axon specification and synaptic activity, phenotypes that are also regulated by Reelin signaling. However, little is known about the role of CLASP2 and its association with the Reelin signaling pathway in the developing brain. Therefore, our goal is to understand how Reelin signaling regulates CLASP2-mediated cytoskeletal function during neuronal and brain development. In the first aim, we will define the interaction of CLASP2 with Dab1, a downstream node in the Reelin pathway, and then determine the functional consequences of this interaction. In the second aim, we will define the in vivo function of CLASP2 during brain development. The proposed studies aim to advance the understanding of how Reelin controls neuronal migration through cytoskeleton reorganization, key elements of normal brain development.